DocBook: The Definitive Guide By Norman Walsh & Leonard Muellner 1st Edition October 1999 1-56592-580-7, Order Number: 5807 652 pages, $36.95 , Includes CD-ROM

DocBook: The Definitive Guide
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Optional

Name

Optional -- Optional information

Synopsis

Mixed Content Model

Optional ::=
((#PCDATA|Link|OLink|ULink|Action|Application|ClassName|Command|
  ComputerOutput|Database|Email|EnVar|ErrorCode|ErrorName|
  ErrorType|Filename|Function|GUIButton|GUIIcon|GUILabel|GUIMenu|
  GUIMenuItem|GUISubmenu|Hardware|Interface|InterfaceDefinition|
  KeyCap|KeyCode|KeyCombo|KeySym|Literal|Constant|Markup|
  MediaLabel|MenuChoice|MouseButton|MsgText|Option|Optional|
  Parameter|Prompt|Property|Replaceable|ReturnValue|SGMLTag|
  StructField|StructName|Symbol|SystemItem|Token|Type|UserInput|
  VarName|Anchor|Comment|Subscript|Superscript|InlineGraphic|
  InlineMediaObject|IndexTerm)+)

Attributes

Common attributes

Tag Minimization

Both the start- and end-tags are required for this element.

Parameter Entities

%cptr.char.mix;	%ndxterm.char.mix;	%para.char.mix;
%programlisting.content;	%refinline.char.mix;	%refname.char.mix;
%screen.content;	%tbl.entry.mdl;	%tech.char.class;
%title.char.mix;

Description

The Optional element indicates that a specified argument, option, or other text is optional. The precise meaning of "optional" varies according to the application or process begin documented.

Processing expectations

Formatted inline.

Optional arguments in a Synopsis are usually given special typographic treatment, often they are surrounded by square brackets. The Optional tag is expected to generate the brackets.

Outside a Synopsis, the typographic treatment of Optional is application-specific.

 Future Changes

The InterfaceDefinition element will be discarded in DocBook V4.0. It will no longer be available in the content model of this element.

Parents

These elements contain Optional: Action, Application, Attribution, BiblioMisc, BridgeHead, Citation, CiteTitle, Command, Comment, ComputerOutput, Database, Emphasis, entry, Filename, ForeignPhrase, FuncParams, FuncSynopsisInfo, Function, GlossSee, GlossSeeAlso, GlossTerm, Hardware, Interface, InterfaceDefinition, KeyCap, LineAnnotation, Link, Literal, LiteralLayout, LoTentry, Member, MsgAud, OLink, Option, Optional, Para, Parameter, Phrase, Primary, PrimaryIE, ProductName, ProgramListing, Property, Quote, RefDescriptor, RefEntryTitle, RefName, RefPurpose, Replaceable, Screen, ScreenInfo, Secondary, SecondaryIE, See, SeeAlso, SeeAlsoIE, SeeIE, Seg, SegTitle, SimPara, Subtitle, Synopsis, SystemItem, Term, Tertiary, TertiaryIE, Title, TitleAbbrev, ToCback, ToCentry, ToCfront, Trademark, ULink, UserInput.

Children

The following elements occur in Optional: Action, Anchor, Application, ClassName, Command, Comment, ComputerOutput, Constant, Database, Email, EnVar, ErrorCode, ErrorName, ErrorType, Filename, Function, GUIButton, GUIIcon, GUILabel, GUIMenu, GUIMenuItem, GUISubmenu, Hardware, IndexTerm, InlineGraphic, InlineMediaObject, Interface, InterfaceDefinition, KeyCap, KeyCode, KeyCombo, KeySym, Link, Literal, Markup, MediaLabel, MenuChoice, MouseButton, MsgText, OLink, Option, Optional, Parameter, Prompt, Property, Replaceable, ReturnValue, SGMLTag, StructField, StructName, Subscript, Superscript, Symbol, SystemItem, Token, Type, ULink, UserInput, VarName.

In some contexts, the following elements are allowed anywhere: BeginPage, IndexTerm.

In some contexts, the following elements are excluded: IndexTerm.

See Also

ComputerOutput, Constant, Literal, Markup, Option, Parameter, Prompt, Replaceable, SGMLTag, UserInput, VarName

Examples

The UNIX ls command could be documented as follows:

<!DOCTYPE synopsis PUBLIC "-//OASIS//DTD DocBook V3.1//EN">
<synopsis>
ls <optional><option>-abcCdfFgilLmnopqrRstux1</option></optional>
   <optional>names</optional>
</synopsis>

ls [-abcCdfFgilLmnopqrRstux1]
   [names]

which might generate the following output:

ls [ -abcCdfFgilLmnopqrRstux1 ] 
   [names]

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